- You can hold your breath (1 + Constitution modifier) minutes, minimum of 30sec.
- After running out of air, you have a number of rounds (6 sec each) equal to your Constitution modifier, with the minimum being 1 round.
- After the previous step, drop to 0 hp. You are dying and cannot regain hp or stabilize until you can breathe again.
When adventurers pursue sahuagin back to their undersea homes, fight off sharks in an ancient shipwreck, or find themselves in a flooded dungeon room, they must fight in a challenging environment. Underwater the following rules apply.
When making a melee weapon attack, a creature that doesn’t have a swimming speed (either natural or granted by magic) has disadvantage on the attack roll unless the weapon is a dagger, javelin, shortsword, spear, or trident.
A ranged weapon attack automatically misses a target beyond the weapon’s normal range. Even against a target within normal range, the attack roll has disadvantage unless the weapon is a crossbow, a net, or a weapon that is thrown like a javelin (including a spear, trident, or dart).
Creatures and objects that are fully immersed in water have resistance to fire damage.